Music in the Round #14 Page 2
More power play
I've bent your ears about AC power gadgets before. It's important, and I have reason to be a bit paranoid about it. The arrival of very hot weather in early June adds voltage sags to my concerns about line noise, adequate current, and surge protection. As I mentioned in this column in May, my first line of defense was a whole-house surge protector. By installing it in the garage, closer to my house's main ground than to any other AC devices, I maximized the probability that surges would take that path of least resistance and spare my valuable components. Many whole-house protection devices are available, and most electricians will be happy to inexpensively install one. My electrician quoted $150 for a SquareD device, labor included.
To my electrician's amusement, I asked him to also install an Environmental Potentials EP-2050 Waveform Correction Absorber ($500). This fancily named gadget provides protection from AC-borne noise by means of a tracking filter, and from damaging voltages by clamping and absorbing surges and dissipating them as heat. It does this without a large inductance that can be saturated in use, but nonetheless maintains a low impedance path (less than 1 ohm) for noise and surge voltages. In addition to its proprietary tracking-filter and surge-absorption circuitry, the EP-2050 apparently uses a device that has been castigated by some for its mortality, but championed by others as the most rapid voltage-clamping device: the MOV (Metal-Oxide Varistor). The EP-2050's circuitry smooths and absorbs current pulses that the MOV might generate, and its two LEDs monitor the MOV's functional integrity.
Does it work? Fortunately, neither nature nor the power company has so far provided a critical test of the EP-2050's protection function, but an examination of my house's line voltage on an oscilloscope revealed a smoother, cleaner 60Hz signal than before. I could not detect anything on the amplifier output, but that's as I would expect. Nonetheless, the EP-2050's LEDs give me great reassurance every time I'm in the garage.
Up in the music room, however, a few voltage sags were sufficient to trigger the undervoltage protection of the Panamax M5510 and M4400-20A that supply AC power to my system. The Panamax power protection did its job of "Protect or Disconnect," and while the room lights only blinked, the system shut down! Considerations of an uninterruptible power supply (UPS) began to dance in my head. Consumer UPS boxes have been around since the PC revolution, but few can put out a smooth sinewave. Most do no better than a coarsely stepped approximation or, worse, a square or triangular waveform. Switching power supplies, common in computers, often like the latter, but the linear power supplies of most audio components do not, and the home theater craze has stimulated many manufacturers to develop more suitable UPS boxes.
Belkin, way back, was a rack-jobber of cables and gadgets. They have since grown into a monster (so to speak), offering almost every imaginable electronic accessory and connector for computers, audio and video systems, and video games. At the 2005 Consumer Electronics and Home Entertainment shows Belkin unveiled Pure/AV, a line of premium products specifically focused on home theater and audio systems. The line includes A/V interconnects, power conditioners and filters, and video processors. Their Home Theater Battery Backup with AVR Technology ($599.99) offers sinewave battery backup, surge protection (5500 joules), and automatic voltage regulation (120VAC, ±8%). It has surge-protection in/outs for three A/V coaxial lines, a phone line, and a network connector. Six UPS/AVR AC outlets and two surge-protected-only AC outlets are provided. Total capacity is 1200VA/640W, and the backup time is up to 40 minutes, depending on load. Full specs are available at www.pureav.com.
After an 8-hour initial battery charge, the HTBB passed all the self and manual tests, so I hooked it up to run everything in the system except the subwoofer, power amp, and plasma monitor. There were not enough AC receptacles for those items, and they would have exceeded the HTBB's recommended load. Besides, in the case of a sag, I'd rather have the power amp recycling while the source components remain on, to prevent loud source-switching pulses being sent through the speakers.
My system's noise level seemed a bit higher than with the Panamaxes, but the overall level of performance was as before. The Belkin's load gauge read 50% when I bit my lip and pulled the HTBB's captive power cable from the wall outlet. Lo and behold, the system kept playing merrily without so much as a burp from the speakers. A small indicator confirmed that the HTBB had switched to battery power. The music kept playing for 20 minutes or so as I watched the battery gauge decline. Then, before the HTBB could be completely exhausted, I plugged it back in. Had it been a real emergency, I'd have noticed the loss of other utilities and had plenty of time to safely shut down my system. Had it been a brownout or a brief interruption in power, I might not have noticed at all—especially as I'd defeated the HTBB's optional audible alarms.
The only faults I could find were that the HTBB vibrated briefly when powered up, then hummed a bit. It hummed a bit more when on battery power. It also ran slightly warm, with or without a load. Belkin's documentation says nothing about AC filtering or noise isolation between the outlets, so the HTBB is evidently not a full-service power-management system. The Pure/AV line includes switching and filtering devices that match the HTBB's elegant appearance and that should reduce the line noise and chassis hum. Overall, Belkin's Pure/AV Home Theater Battery Backup with AVR Technology looks good, does the job, and, with a little Googling, can be found for less than its $600 list price. Just make sure that the current and load ratings match your needs; the AVR load is limited to 85% of total capacity.
The American Power Conversion S15 is another story. APC is the leader in the uninterruptible-power-supply business, but the S15 is their first foray into the high end. At more than 57 lbs, the S-15 is as hefty as most power amps, and has a capacity of 1440VA/900W with a battery life of 7.5 minutes (full load) or 20 minutes (half load). The S15's larger rated load makes for shorter quoted times than for the Belkin unit, but in practice it lasted a lot longer. What further distinguishes the APC S15 from the Pure/AV HTBB is the former's wider range of features and controls, as well as extensible external power and isolated EMI/RFI filtration for each of its outlet banks. The S15 is a comprehensive power source, conditioner, and controller, and costs $1499.
Clustered around the S15's front-panel display are LED indicators and four buttons for Status, Setup, and Up/Down navigation. The two-line alphanumeric display is used to set up audible alarms, delayed power up/down, thresholds for over/under voltage, etc., and to display in/out voltage, in/out frequency, battery status, load/runtime, serial number, technical-support URL and phone number, etc. Plug it in and turn it on, and it goes through a fascinating series of self-tests, all revealed onscreen.
The S15's rear panel sports 12 AC outlets in four banks, each bank physically and electrically isolated, with surge protection, voltage regulation, filtering, and battery backup on all lines. Surges are limited to no more than 40V over normal line voltage—much lower than the more common 330V threshold. Also on the rear are a port for an external battery, a data port for logging/control, filter modular in/outs for data and phone lines, coax in/outs for antenna, satellite, and cable modem lines, a DC trigger in/out, a circuit breaker, and an IEC cable receptacle. The phone and cable in/outs include splitters. Finally, there's a ventilation fan, a substantial ground terminal, and a wiring-fault LED. If the last lights up, your building wiring is faulty (missing ground, reversed polarity, etc.) and should be corrected by a qualified electrician.
The S15 has too many features to detail here, but I must mention that the voltage regulation is accomplished electronically and without the hysteresis or rebound problems associated with slower, motor-driven compensation. I used the S15 in my main city system: loudspeakers and power amps at one end, the rest of the electronics at the other. I connected the S15 to various combinations of power amplifiers running, at high levels, either three Revel Studio or two B&W 802D speakers. The power amps were the Bel Canto eVo6, the Simaudio Moon W-8, and the Classé Omicron monoblocks—heavy loads indeed.
The S15 didn't care. Whether running the 300W Omicrons or the 250Wpc W-8, or even the W-8 and the eVo6 together, the sound was as tight and powerful as it was with direct AC feed from the wall. Furthermore, yanking the cable from the wall made absolutely no difference. APC had said the S15 could run the eVo6 for 95 minutes, the W-8 for 110 minutes, or both for 72 minutes, and though I ran each of them for less than an hour, I believe it. Perhaps I'm narrow-minded, but I didn't expect any magical transformations in the sound—all competent electronic components should be capable of optimum performance with clean AC. Still, the eVo6 loved being run off the S15. Gone was that nearly subliminal gray coloration in the upper midrange, as well as the intermittent chassis vibration that seemed to be the Bel Canto's response to low line voltage. For all my protestations that I was into power conditioning solely for reasons of safety and security, the S15 made the bridged eVo6 into an even better power amplifier—a super amp.
There was just one thing: noise. With all three amps, the noise I heard when I put my ear to a speaker's tweeter was greatly reduced when they were running off the APC S-15. I know some noise is always there, but if it can be detected only within 6" of the tweeter, that's okay. However, at the suggestion of Environmental Potentials' Doug Joseph, and to satisfy my own curiosity, I connected an EP-2450 Home Theater Power Supply ($800) between the S-15 and the amps. This lightweight, full-size chassis has eight unisolated AC outlets, which can pass 20 amperes of HF-filtered, ground-filtered, surge-protected AC. It also has a filtered and surge-protected coaxial line. It ain't cheap, but dammit, it reduced amp noise to effective inaudibility! With any of the three amps, I had to put my ear right on the tweeter shield of a B&W 802D—and even then, I often wasn't certain I heard anything. Whatever noise there was was below the noise floor of the room, and quieter than I have ever heard—or not heard. Not only that, but the EP-2450 performed the same trick with the noisier Belkin HTBB.
Of course, knowing this, I subsequently found both systems sounded cleaner and more detailed at low levels with the EP-2450, but that's a biased observation. If, despite other efforts, you're still troubled by HF noise, particularly with high-sensitivity speakers, the EP-2450 might just be what you need.
Next time in the Round
I'd promised a report on Rocket's R-DES parametric subwoofer equalizer, but things go awry with even the best of efforts. I had some trouble with an early sample I got at the 2005 Consumer Electronics Show, and although it ain't clear whether the unit or my use is at fault, another has just arrived. Other things in the pipeline include a multichannel power amp, yet another universal disc player, and, briefly, further adventures with the APC and EP units in Connecticut. And lots more multichannel music.